Refractory article



UNITED STATES PATEN OFFICE.

SILAS C. LINBARG-EB, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO THE CARBO-RUNDUM COMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF .NoDrawing.

I T all whom it may cofi'oern:

Be it known that I, SILAS C. LINBAnGER, a citizen of the United. States,residing at Niagara Falls, in the county of Niagara and State of NewYork, have invented a new and useful Improvement in RefractoryArticles,- of which the following is a full, clear, and

exact description.

The present invention relates particularly to an improved refractoryarticle, andmore particularly to a glazed refractory used to support.white' ware, china, porcelain or other ceramic products during thebiscuit or I glost firings.

- The principal object'of the present invention is to provide arefractory or saggar of the type referredto, in which Ware may be burnedwithout producing discoloration thereof. I

A still further object of the present 1nvention is to provide a glostkiln refractory composed of silicon carbid, or carborundum, andhavingthe surface thereof protected by a coating of vitrified orimpervious material to prevent. discoloration of wars burned therein.

The foregoing and other objects, together with their attendantadvantages, will be apparent as the invention becomes better understoodby reference to athe accompanying specification, itbeing premised thatchanges may be'made in the ingredients used, and in the proportionsemployed, within the scope f from the action of the hot gases of thekiln,

of the appended claims without departing from the spirit of theinvention.

It has been shown that saggars and kiln refractories of the type usedin'the setting and supporting of ceramic wares during the firing processmaybe made much superior by the utilization of silicon carbid therein,

carbid are superior to the ordinary clay saggars due to the increasedmechanical strength, increased heat conductivity and increasedresistance to sudden temperature changes. .When ceramic materials, andespecially the finer wares, such as white ware, china, porcelain and thelike are fired in close proximity to saggars .or refractories containingsilicon carbid, it has been found that there may be an objectionableblackenin or discoloration of the white or light co ored ware due to thedecomposition of the silicon carbid employed.

Refractories containing a large percent- PENNSYLVANIA. v nnraao'roayARTICLE.

Specification of Letters Patent. P t t t, 1 1 Application fil ed June21, 1919.. Serial No. 305,868.

age of silicon carbid usually produce a detrimental discoloration'of theware contained therein during the first firing. Ordinarily,

eralfactors. Among these is the percentage Of SlllCOIl carbid in themixture, the fineness of the grain of the silicon carbid used, the

temperature at which the ware is fired, and the kiln-atmosyi hereprevailing during the firing period. he discoloration in each of theabove instances increases with the ercentage of silicon-carbid employed,the neness of the grain and the temperatures to which the Ware and therefractories are sub- 'ected. 3 Experiment has shown that this lackeningor discoloration of the Ware'is due to the dissociation or oxidation ofthe silicon carbid crystals in the refractories.

A close study of a .piece of refractory material composed of a highercentage of silicon carbid with a clay bin er, which has been fired asuflicient number of times to substantially eliminate the blackeningeffect so pronounced in the first burn, shows that an impervious crustor glaze has been, produced on the surface thereof. This glaze protectsthe crystals of the silicon .carbid or furnace. atmosphere, and preventsany further decomposition of the same, and the resulting discolorationof the ware. The glaze formed is probably due' to the oxidation-of thesilicon carbid into silicon dioxid and carbon monoxid or carbon dioxid.The

silicon dioxid so formed reacts with the clay blnder of the refractoryforming amixture which vltrifies or fuses into a protective thoughthematerial is fired to temperatures in. excess of 1350-.C. Such a glazemay be applied to the refractories by the application of well knownceramic principles and successfully overcomes the blackening effect ordiscoloration in the first firing of the re-. fractories.

Most glazes contain a high alkali content.-

Flint 1100 parts Clay 800 parts Spar 10 parts Whiting 10 parts In aglaze having the above composition it will be noted that the alkalicontent is very low. In the particular composition referred to, thefluxing ingredients of the glaze constitute approximately 1.04%, therebygiving a total alkali content of .0036 molecular equivalents. It will beunderstood that the above batch weights are merely given as anillustration, and that the same i can be varled to meet the preciseconditions encountered during the firing of the ware.

The glaze or coating used may be applied to the green refractory afterit has been dried, as is done in the well known terra cotta process,andsubsequently fired in kilns at a sufficiently high temperature tomature both the body and the glaze in one firing. This may be broughtabout either in a ceramic kiln, or in the structure in which therefractory shape is to be used. If desired, however, the glaze may beapplied in a slip or fluid condition by any ofthe well known meansemployed in glazing ware, after it has been first fired to its maturingtemperature. 'When this method is employed, the whole structure is thensubjected to a temperature such thatrthe glaze will be matured and willfirmly adhere to the main body of the refractory.-

It will be apparent that the type of glaze employed may be varied atwill, it being desirable only to produce a glaze having a low alkalicontent and capable of resisting temperatures inexcess of 1350 0. Anycombination of clays, or clay substances, or a combination thereof withsilica and a fluxing material may be advantageously employed. Thecombination and proportions.

of the various ingredients is such that an impervious coating is formedon the surface of the silicon carbid refractoryatthe maturingtemperature thereof and having a sufficiently long vitrification rangeso that it will not flow or boil t any temperature below that at whichth ware 'containe therein is fired. By experiment ,I have found that thealkali-content, where practical, should not exceed 2% of the entirecomposition.

I claim:

1. A refractory article 'for use in firing ceramic ware to preventdiscoloration thereof, comprising a body containing silicon carbid, anda protective coating free from silicon carbid formed thereon,substantially as described. a I g 2. A refractory article for use infiring ceramic ware to prevent discoloration thereof, comprising a bodycontaining silicon carbid, and a protective coating free from" siliconcarbid and com rising a refractory glaze, substantially as escribed. v

3. A refractory article for use infiring ceramic ware to preventdiscoloration thereof, comprising a bodycontaining carborundum, and aprotective coating free from silicon carbid applied thereto and 'comprising a refractory glaze having a high viscosity, substantially asdescribed.

contains silicon carbid and havinga coating free from silicon carbid andcomprlsing a refractory glaze with a fusion point ex-' 4. A refractoryarticle, the body of which contains silicon carbid and having a coatingfree from silicon carbid and comprising'a [glaze having refractoryproperties capable of preventin superficial dissociation of the siliconcarbi substantially as described.

'8. A refractory article, the body of which .contains silicon carbid andhaving a coating free from silicon carbid and comprising a refractoryglaze having a'low alkali content, substantially as described.

In testimony whereof, set my hand.

SILAS c. LINBARGER.

I have hereunto

